For washing wafers, etc., in the process of the production of semiconductor devices of silicon and compounds such as GaAs or in the process of the production of liquid crystal devices (LCD), and for removing dry-etching residual substance (residue) in the above processes, there are used strong acids (hydrochloric acid, sulfuric acid, nitric acid and fluoric acid), strong alkalis (sodium hydroxide, ammonia, hydrazine and hydroxylamine), ammonium fluoride, alkanolamines, organic solvents, and the like.
The above substances are all deleterious substances or hazardous substances and involve many problems in respect of working and environmental safety.
More specifically, for the removal of impurity ion, particles, an organic substance and an oxide layer on a metal (including a semimetal such as silicon) surface or a glass surface of a wafer, etc., in the above processes, there is required a complicated process (so-called RCA process) according to an object to be removed, in which a chemical such as a strong acid, a strong alkali or the like is used depending upon the object and cleaning is repeated. These chemicals involve problems in respect of both operability and safety.
For removing a dry etching residue, further, there is used hydroxylamine, tetramethylammonium hydroxide (TMAH), ammonium fluoride, alkanolamine, a mixture of an organic solvent with any one of these compounds, or an organic solvent itself, while these compounds have a problem in view of working safety or environmental pollution. Further, when the material of an object to be treated is a metal, the above compounds have another problem that they remain in the metal to corrode the metal.